Q. The buffer action of blood is due to the presence of:
Answer: HCO3(–) and H2CO3
Notes: The most important buffer for maintaining acid-base balance in the blood is the carbonic-acid-bicarbonate buffer. Three different buffer systems exist in blood, the bicarbonate buffer and the phosphate buffer are composed of "simple" chemicals. In addition the carbonyl groups (-COOH) and the amide group (-NH2) present on proteins allow some of these to act as buffers.

• H2CO3 + H2O <—> HCO3(–) +H3O(+)
• H2PO4(–) + H2O <—> HPO4(2–) + H3O(+)